Title: Hormone Therapy and Cognitive Aging in Older and Younger Postmenopausal Women: Extension Study of WHIMS-ECHO and WHIMS-Y[unreadable] The Women[unreadable]s Health Initiative (WHI) randomized clinical trials of hormone therapy (HT) were designed to determine whether HT had beneficial effects on health outcomes, especially cardiovascular health, in postmenopausal women. Women without uteri were randomly assigned to take one daily tablet containing either conjugated equine estrogens (CEE), 0.625 mg (Premarin, Wyeth Pharmaceuticals), or a matching placebo, and women with uteri were randomly assigned to take one daily tablet containing either CEE, 0.625 mg, and medroxyprogesterone acetate (MPA), 2.5 mg, (Prempro, Wyeth Pharmaceuticals) or a matching placebo. The WHI Memory Study (WHIMS) was an ancillaryto the WHI and investigated the effects of HT on risk of probable dementia and any cognitive impairment and on changes in global cognition over time. The WHI and ancillary WHIMS study were stopped earlier than planned for both the combination therapy (in 2002) and CEE-Alone (in 2004) because these treatments increased health risks and did not protect against coronary heart disease. Although study medications were discontinued, follow-up assessments continued. The purpose of the present contract is to continue prospective follow-ups, including dementia screening and cognitive assessments, of women in the WHIMS Epidemiology of Cognitive Health Outcomes (WHIMS-ECHO) cohort In addition, this contract continues prospective cognitive assessments in the more recently initiated Women[unreadable]s Health Initiative Memory Study of Younger Women (WHIMS-Y) to determine the long-term impact of random assignment to postmenopausal HT among women who were 50-54 years of age at the time they were randomized in the WHI hormone trials. WHIMS-Y tests the [unreadable]window of opportunity[unreadable] hypothesis that HT shortly after menopause will confer benefit to later cognitive health.